<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>css相关的作业</title>
    <style type="text/css">
        div{
            background-color: orange;
            width: 300px;
            height: 300px;
            padding: 20px;
            border: dashed 20px;
        }
    </style>
</head>
<body>
<div>我的世界</div>
</body>
</html>